It has long been known to use various peroxides as initiators for the free radical catalytic polymerization of low molecular weight materials to form polymers. These polymerizations are performed with a wide variety of starting materials to form many useful polymers that have numerous desirable properties which depend upon the nature of the starting material, the degree of polymerization, the extent of branching and the extent of crosslinking.
More recently it has been discovered that various cyclobutarene containing materials can be induced to undergo polymerization by subjecting these to elevated temperatures. Since these reactions consume the cyclobutarene moiety, useful materials often are biscyclobutarenes in which two cyclobutarene moieties are connected by various bridging or linking groups or structures. Low molecular weight materials containing two cyclobutarene moieties can polymerize linearly through ring opening polymerization reactions of the two cyclobutarene moieties.
If an average of more than two polymerizable functionalities are included per unit of starting material, branching and crosslinking reactions are possible. These reaction types are also attainable through the use of multiple polymerization mechanisms.
A process is disclosed in U.S. Pat. No. 4,708,990 wherein a living polymer of the alkenyl type is end-capped with an arylcyclobutene monomer end-capping agent. Secondary polymerization of the polymer can then be induced by heating. Cyclobutarene moieties have been incorporated in polymers through reactions involving cyclobutarene monomers containing alkylenic unsaturation, as, for example, in U.S. Pat. No. 4,698,394.
It is highly desirable to have a multifunctional monomeric material which can be used as an initiator to catalyze free radical polymerizations wherein the material fragments of the initiator are incorporated in the polymer, and which fragments can subsequently be induced to participate in other polymerizations or reactions. It would be particularly desirable to be able to differentiate and control the extent of the various reactions by means of some easily controlable reaction parameter such as temperature.